Manufacture of nickel powder



Sept, 9, 1958 E. OESTREICHER'ETAL 5 MANUFACTURE OF NICKEL POWDER Filed Sept. 21, 1956 WITHDRAWAL OF CO CARBONYL VAPOR FILTER I2 I4 9 HEATING l l WITHDRAWAL OF METAL INVENTORS ERNST OESTREICHER LEO SCHLECHT United States Patent Oflice MANUFACTURE OF NICKEL POWDER Ernst Oestreicher, Ludwigshafen (Rhine) Oppau, and

Leo Schlecht, Ludwigshafen (Rhine), Germany, assignors to Badische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen (Rhine), Germany This invention relates to the production of nickel powder by thermal decomposition of nickel carbonyl and, particularly, to the production of nickel powder having an extremely small particle size.

This application is a continuation-in-part of our copending application Serial Number 198,031, filed November 28, 1950, and now abandoned.

Nickel powder having a very small particle size, especially below 6 microns, affords considerable advantages in powder metallurgical applications. The fine powders sinter at low temperatures, and sintered articles are produced which, unlike sintered articles made from coarser powders, can be transformed without difficulty by pressure methods, such as hammering or rolling, into semifinished products without the formation of undesirable cracks. The fine powders markedly facilitate the formation of alloys with other metal powders, enabling the rapid production of homogeneous alloys and, where desired, a high pore volume.

The principal object of this invention is to provide an improved method or process for producing nickel powder having a particle size which does not exceed 6 microns and, particularly, to avoid the special measures which were previously required and provide a very simple process which markedly increases the quantity of fine powder produced. Preferably, more than about 80 percent by weight of the particles do not exceed microns.

- the decomposition space,

2,851,348 Patented Sept. 9, 1958 Part of the heat required may be supplied directly in and at least part is supplied through the wall of the decomposition chamber. The heat supplied through the wall of the chamber is supplied in such a manner that the temperature of the inner surface of the wall is above the decomposition temperature of the carbonyl but not substantially higher than the decomposition temperature of carbon monoxide. Prior to the invention, processes have been proposed for producingfinely divided nickel from carbonyl vapor, wherein vaporous nickel carbonyl was introduced into a chamber externally heated to temperatures above the decomposition temperature of the carbonyl, the decomposition taking place substantially in the hot free space of the chamber at a distance from the hot walls of the chamber. In this manner, nickel was produced having a particle size predominantly between 2 and 10 microns, with a considerable proportion larger than 5 microns. To produce the powder not greater than 6, preferably not greater than 5, microns in particle size as desired for various purposes, several methods have been proposed. For example, one method involved the dilution of the carbonyl vapor with thirty or more volumes of carbon monoxide. In this manner, there was an effect on size due to dilution and the gases passed through the decomposition chamber at or more times the speed of the gases when carbonyl vapor alone was supplied to the chamber. Another method involved applying reduced pressure from the chamber exit, for example, down to 20 millimeters of mercury, which correspondingly increased the speed of passage of the materials The invention is particularly concerned with the production of nickel powder by thermal decomposition of nickel carbonyl vapor in the hot free space of a decomposition chamber or vessel. In accordance with the invention, the surprising discovery has been made that nickel powder in which the particle 'size'of substantially all of the particles does not exceed 6 microns, and in which the particle size of more than about 85 percent by weight of the particles does not exceed 5 microns is produced by decomposing more than 37 kilograms per hour of metal carbonyl per cubic meter of decomposition space. The decomposition temperature is maintained within the range of 200 C. to 300 C. In this manner,

the quantity produced is much greater than by prior methods.

In the same manner, nickel powder in which the particle size of at least about 95 percent by weight of the particles does not exceed Sqmicrons is obtained by decomposing at least about 43 kilograms per hourof nickel carbonylper cubic meter of decomposition space. A further decomposition rate and particle size maximum are about 49 kg./hr./m. for 3 microns maximum. By reference to substantially all of the particles is meant at least about 95%.

"The temperature in the decomposition space is maintained within the range of 200 C. to 300 C., to produce the desired low carbon content and other desirable properties. Preferably, the decomposition temperature is maintained within the range of 230 C. to 280 C., and it is further preferred to carry out the decomposition at about 260 C. to 270 C.

through the chamber. Also, it was proposed to limit the time of the metal particles in the decomposition zone to 20 seconds. These measures, while producing fine particles, are limited by the low quantitative production of metal powder. They also require special measures for carrying out the decomposition, for recovering the metal powder, and for purifying the metal powder, especially when undecomposed carbonyl remains.

The process, of the invention may be carried out in an apparatus, such as that illustrated in the accompanying drawing. There, a decomposition chamber 4 is illustrated which is heated by a hollow jacket 2 surrounding the chamber through which heating gases circulate. The heat necessary for the decomposition of metal carbonyl is produced in an oil or gasburner 5 into which oil or gases to be burnt are introduced through a pipe 7. The hot gases then are introduced into the jacket 2 through a pipe 8, and are led around the chamber by means of battle plates 3 and drawn off at the lower part of the jacket by means of a blower 6, from which the gases are recycled into the burner 5 in order to be heated again. The nickel carbonyl vapor is introduced into the chamber through a pipe 1 and is decomposed into nickel powder and carbon monoxide. The carbon monoxide is withdrawn from the chamber through lines 9, 11 and 13. Particles of nickel powder which are entrained by the gases leaving the chamber are separated from the gas by means of a filter 12 and withdrawn through a valve 10. From the chamber the nickel powder is drawn oif through a valve 14.

In the present invention, it is necessary to insure that sufficient heat be supplied to the decomposition space in the chamber to substantially completely decompose the quantity of more than 37 kilograms of nickel carbonyl per hour per cubic meter supplied to the chamber. In

providing this large quantity of heat to the interior, to

produce carbon by decomposition of carbon monoxide.

In other words, the temperature differential, or At, from the inner wall to the interior of the decomposition space is not raised, but the quantity of heat transmitted to the space is increased. This is accomplished, for example, by supplying a greater quantityof heating gases to the jacket, but at no higher temperature. Alternatively, the heat transmitting surface of the chamber wall may be enlarged, or a more conductive material may be employed in the construction of the wall.

An important advantage of the invention is that the decomposition may be carried out at about atmospheric pressure, that is, at the pressure existing in the system when the gases exit to atmospheric pressure with no application of reduced or increased pressure.

The following examples illustrate the invention and also illustrate the surprising and unexpected nature thereof, but it is to be understood that the invention is not limited to the specific conditions and procedures set forth therein, which are only illustrative.

Example 1 A decomposition chamber, such as that illustrated in the drawing at 4, was provided which had an inner diameter of 1 meter and a length of meters, and which was surrounded with the jacket 2 for heating the chamber by the circulation of hot gases in the jacket. The hot gases came from the burner 5, recycling the cooler spent heating gases leaving the jacket to the burner by the blower 6. The temperature in the decomposition space was thus maintained at about 260 C.

148 kilograms of nickel tetracarbonyl vapor were supplied to the decomposition chamber per hour. This was equivalent to a throughput of about 37 kilograms per hour per cubic meter of decomposition space. The gases exited to substantially atmospheric pressure. 1200 kilograms of a nickel powder having the following particle size distribution was obtained in 24 hours:

50% 3 microns and below.

35% 3-5 microns.

15% 5-6 microns.

Example 2 In the manner described in Example 1, 172 kilograms of nickel carbonyl were supplied to the decomposition chamber per hour. This corresponded to a supply of about 43 kilograms per hour per cubic meter of decomposition space. The gases left the chamber to substantially atmospheric pressure. The heating gas supplied to the jacket was at the same temperature as before, but the quantity of heating gas supplied was increased by about 15%, by increasing the delivery of the blower 6 and the output of the burner 5. The temperature of the decomposition space was about the same as in Example l.

l400 kilograms of a much finer powder was obtained in 24 hours, having the following particle size distribution:

72% 3 microns and below.

25% 3-5 microns.

3% Above 5 microns to 6 microns.

Example 3 In the manner described in Example 1, l96 kilograms of nickel carbonyl were supplied to the decomposition chamber per hour. This corresponded to a supply of about 49 kilograms per hour per cubic meter of decomposition space. The gases left the chamber to substantially atmospheric pressure. The heating gas supplied to the jacket was at the same temperature as before, but the quantity of heating gas supplied was increased by about 15% over Example 2, by increasing the delivery of the blower 6 and the output of the burner 5. The

4 temperature of the decomposition space was about the same as in Example 1.

1600 kilograms of a much finer powder was obtained in 24 hours, having the following particle size distribution:

% 3 microns and below. 5% 3-5 microns. 0 Above 5 microns.

The invention thus embodies the discovery of a new phenomenon and condition in the production of fine nickel powder, that the nickel carbonyl be decomposed and nickel powder be produced in hitherto unknown quantities per unit of time and volume. The invention provides a great increase in the production of the very fine nickel powders, by an exceptionally simple and very reliable method. The powders can be used without further treatment for powder metallurgical and other purposes.

We claim:

1. In the production of nickel powder by thermal decomposition of nickel carbonyl vapor in the hot free space of a decomposition chamber, the improvement for producing nickel powder in which the particle size of substantially all of the particles does not exceed 6 microns which comprises supplying at least about 37 kilograms per hour of nickel carbonyl per cubic meter of decomposition space to said free space, and substantially completely decomposing said quantity of nickel carbonyl therein, by maintaining the decomposition temperature within the range of 200 C. to 300 C. and supplying suflicient heat to said free space to produce said complete decomposition within said temperature range.

2. In the production of nickel powder by thermal decomposition of nickel carbonyl vapor in the hot free space of a decomposition chamber, the improvement for producing nickel powder in which the particles size of at least 95 percent by weight of the particles does not exceed 5 microns which comprises supplying at least about 43 kilograms per hour of nickel carbonyl per cubic meter of decomposition space to said free space, and substantially completely decomposing said quantity of nickel carbonyl therein, by maintaining the decomposition temperature within the range of 200 C. to 300 C. and supplying suflicient heat to said free space to produce said complete decomposition within said temperature range.

3. In the production of nickel powder by thermal decomposition of nickel carbonyl vapor in the hot free space of a decomposition chamber, the improvement for producing nickel powder in which the particle size of at least about 95 percent by weight of the particles does not exceed 5 microns which comprises supplying at least about 43 kilograms per hour of nickel carbonyl per cubic meter of decomposition space to said free space at about atmospheric pressure, and substantially completely decomposing said quantity of nickel carbonyl therein, by maintaining the decomposition temperature within the range of 200 C. to 300 C. and supplying sufficient heat to said free space to produce said complete decomposition within said temperature range.

4. In the production of nickel powder by thermal decomposition of nickel carbonyl vapor in the hot free space of a decomposition chamber, the improvement for producing nickel powder in which the particle size of at least about 95 percent by weight of the particles does not exceed 5 microns which comprises supplying at least about 43 kilograms per hour of nickel carbonyl per cubic meter of decomposition space to said free space, and substantially completely decomposing said quantity of nickel carbonyl therein, by maintaining the decomposition temperature within the range of 230 C. to 280 C. and supplying sufficient heat to said free space to produce said complete decomposition within said temperature range.

5. In the production 'of nickel powder by thermal decomposition of nickel carbonyl vapor in the hot free space of a decomposition chamber, the improvement for producing nickel powder in which the particle size of at least about 95 percent by weight of the particles does not exceed 3 microns which comprises supplying at least about 49 kilograms per hour of nickel carbonyl per cubic meter of decomposition space to said free space, and substantially completely decomposing said quantity of nicked carbonyl therein, by maintaining the decomposition temperature within the range of 200 C. to 300 C. and supplying sufiicient heat to said free space to produce said complete decomposition within said temperature range, at least part of the heat required being supplied through the wall of said chamber, the temperature of the inner surface of said wall being maintained not substantially higher than the decomposition temperature of carbon monoxide.

6 References Cited in the file of this patent UNITED STATES PATENTS 1,759,661 Muller May 20, 1930 1,836,732 Schlecht et a1. Dec. 15, 1931 2,597,701 Beller May 20, 1952 FOREIGN PATENTS 679,439 Great Britain Sept. 17, 1952 682,897 Great Britain Nov. 19, 1952 684,054 Great Britain Dec. 10, 1952 824,198 Germany Dec. 10, 1951 834,100 Germany Mar. 17, 1952 OTHER REFERENCES Symposium 'On Powder Metallurgy, December 1947, pages 48 and 49; published by the Iron and Steel Insti tute, London, England.

Carbonyl Nickel and Carbonyl Iron Powders. B. I. O. S. Final Report No. 1575, page 17, published in 1947. Distributed by Mapleton House Publishers, Brooklyn, N. Y. 

1. IN THE PRODUCTION OF NICKEL POWDER BY THERMAL DECOMPOSITION OF NICKEL CARBONYL VAPOR IN THE HOT FREE SPACE OF A DECOMPOSITION CHAMBER, THE IMPROVEMENT FOR PRODUCING NICKEL POWDER IN WHICH THE PARTICLE SIZE OF SUBSTANTIALLY ALL OF THE PARTICLES DOES NOT EXCEED 6 MICRONS WHICH COMPRISES SUPPLYING AT LEAST ABOUT 37 KILOGRAMS PER HOUR OF NICKEL CARBONYL PER CUBIC METER OF DECOMPOSITION SPACE TO SAID FREE SPACE, AND SUBSTANTIALLY COMPLETELY DECOMPOSING SAID QUANTITY OF NICKEL CARBONYL THEREIN, BY MAINTAINING THE DECOMPOSITION TEMPERATURE WITHIN THE RANGE OF 200*C. TO 300*C. AND SUPPLYING SUFFICIENT HEAT TO SAID FREE SPACE TO PRODUCE SAID COMPLETE DECOMPOSITION WITHIN SAID TEMPERATURE RANGE. 